Journal of Medical Genetics最新文献

Temple syndrome is an imprinting disorder resulting from abnormal genomic or epigenomic aberrations of chromosome 14 including maternal uniparental disomy (matUPD), paternal deletion of 14q32, or aberrant methylation of the imprinting control regions at 14q32. Understanding the underlying molecular mechanism is essential to understanding the recurrence risk and physical effects. Currently, diagnosis requires the detection of aberrant methylation and copy number loss via methylation-sensitive assays such as methylation-specific multiplex ligation-dependent probe amplification, and short tandem repeat analysis to detect matUPD and the presence of epimutation. Therefore, a one-step approach that can detect aberrant methylation and underlying genetic mechanisms would be of high clinical value. Here we use nanopore sequencing to delineate the molecular diagnosis of a case with Temple syndrome. We demonstrate the application of nanopore sequencing to detect aberrant methylation and underlying genetic mechanisms simultaneously in this case, thus providing a proof of concept for a one-step approach for molecular diagnosis of this disorder.

RNU4-2 encodes U4 small nuclear RNA (snRNA), a non-coding RNA forming the spliceosome complex via the U4/U6 snRNA duplex. RNU4-2 heterozygous variants cause ReNU syndrome, which is characterised by intellectual disability, developmental delay, epilepsy, short stature and distinctive dysmorphic features. ReNU syndrome accounts for 0.4-0.5% of all cases of developmental delay, and RNU4-2 variants are located in the T-loop or stem III region of U4 snRNA, of which approximately 80% are the n.64_65insT variant in the T-loop. We identified four Japanese patients (4.3%) with novel and recurrent RNU4-2 variants from 93 individuals of developmental delay with negative results from exome sequencing. Genotype-phenotype correlations were observed in the present case series and a literature review. T-loop variants manifested severe developmental delay with more than 70% of cases being non-verbal. Stem III region variants resulted in milder developmental delay with fluent speech and nearly normal gross motor development milestones. In addition, we report a patient demonstrating intractable epilepsy with neurological regression harbouring a novel de novo heterozygous RNU4-2 variant (n.66A>G). This report expands the phenotypic spectrum of ReNU syndrome and suggests the presence of phenotypic variability related to variant location.

The aim of this document is to provide an updated statement from the Canadian College of Medical Geneticists (CCMG) regarding the current state and some future considerations on the collection, distribution, and storage of genomic information within electronic health records (EHRs), including which aspects of genomic data might warrant special attention. The original version of this document was written by the CCMG Ethics and Public Policy committee in 2010 based on data collected via an online survey of the CCMG membership at the time. It is updated here to reflect the current state of healthcare in 2024, where EHRs are almost ubiquitously used, and genomic medicine has expanded in its breadth and scope. The document was circulated to the general membership for review and feedback and has been approved by the CCMG Board of Directors.

Biallelic variants in NUP107 cause isolated or syndromic steroid-resistant nephrotic syndrome (SRNS), characterised by proteinuria, hypoalbuminaemia and focal segmental glomerulosclerosis that progresses to end-stage renal disease. Patients with syndromic SRNS have microcephaly, developmental delay or intellectual disability and short stature. Simplified gyration is observed in some individuals. We report on a 2-year-old girl with novel biallelic NUP107 variants, c.2606G>T; p.(Gly869Val) and c.1576+1G>A, proteinuria and a severe neurodevelopmental disorder with microcephaly, developmental delay, early-onset seizures, sensorineural hearing loss and brain structural anomalies, including simplified gyral pattern and hypoplasia of the corpus callosum, pons, brainstem and cerebellum. NUP107 is part of the NUP107-160 complex, which, together with other proteins termed nucleoporins, forms the nuclear pore complex (NPC). The NPC regulates nucleocytoplasmic transport and other cellular processes. In patient-derived fibroblasts, we identified aberrantly spliced NUP107 mRNAs with a frameshift and premature stop codon leading to non-sense-mediated mRNA decay, reduced levels of NUP107 transcripts, reduced NUP107 and NUP133 proteins, and a reduced NPC number. In addition, an abnormal nucleolar morphology was found in patient-derived cells. Our functional data support the conclusion that the NUP107 variants underlie the patient's phenotype, thereby broadening the clinical spectrum associated with NUP107 variants to include abnormal brain development.

We analysed rare variants in the non-coding RNU4-2 gene as a potential cause of neurodevelopmental disorder (NDD) and intellectual disability (ID) in a large cohort of individuals enriched for parental consanguinity.Genome sequencing (GS) data from 22 928 individuals in our Biodatabank were queried for rare, monoallelic variants in RNU4-2 From these, 4918 patients presented with NDD/ID. Human Phenotype Ontology (HPO)-encoded clinical information was extracted and analysed using the ontologyX R package.Nearly 50% of the 4918 patients with NDD/ID reported parental consanguinity. Eight relevant heterozygous RNU4-2 variants were identified in 28 patients. n.64_65insT was the most frequently detected variant (20 patients, 71%), while the remaining variants were found in 1 or 2 patients each (n.65A>G, n.66A>G, n.67A>G, n.70T>C, n.76C>T, n.95C>G and n.135A>C). Four variants are novel or ultra-rare, and two of them are in the 3' stem loops. HPO-based analysis revealed a consistent syndromic phenotype characterised by NDD, abnormal brain morphology, hypotonia, global developmental delay, microcephaly, seizures, atypical behaviour and facial dysmorphism. RNU4-2 variants accounted for approximately 0.55% of NDD/ID cases in our full cohort, and 0.25% in the subset of consanguineous patients (all genetic causes included).This study underscores the significance of RNU4-2 as a major genetic cause of NDD/ID, extending its relevance to consanguineous patients, where recessive disorders are often suspected. We advocate for the re-evaluation of existing GS data to uncover potential diagnoses and emphasise the importance of GS as a first-tier diagnostic test.

Background: The management of women with germline pathogenic variants (GPVs) in breast (BC) and ovarian cancer (OC) susceptibility genes is focused on surveillance and risk-reducing surgery/medication. Most women are assigned an average range of risk and treated accordingly, but it is possible to personalise this. Here, we explore the economic impact of risk personalisation.

Method: We compared two strategies for risk stratification for female participants: conventional risk assessment (CRA), which only involves information from genetic testing and personalised risk assessment (PRA), using genetic and non-genetic risk modifiers. Three different versions of PRA were compared, which were combinations of polygenic risk score and questionnaire-based factors. A patient-level Markov model was designed to estimate the overall National Health Service cost and quality-adjusted life years (QALYs) after risk assessment. Results were given for 20 different groups of women based on their GPV status and family history.

Results: Across the 20 scenarios, the results showed that PRA was cost-effective compared with CRA using a £20 000 per QALY threshold in women with a GPV in PALB2 who have OC or BC+OC family history, and women with a GPV in ATM, CHEK2, RAD51C or RAD51D. For women with a GPV in BRCA1 or BRCA2, women with no pathogenic variant and women with a GPV in PALB2 who have unknown family history or BC family history, CRA was more cost-effective. PRA was cost-effective compared with CRA in specific situations predominantly associated with moderate-risk BC GPVs (RAD51C/RAD51D/CHEK2/ATM), while CRA was cost-effective compared with PRA predominantly with high-risk BC GPVs (BRCA1/BRCA2/PALB2).

Conclusion: PRA was cost-effective in specific situations compared with CRA in the UK for assessment of women with or without GPVs in BC and OC susceptibility genes.

A query was sent to the cancer predisposition gene variant database Cancer Variant Interpretation Group UK, on the nonsense variant in NM_032043.3(BRIP1):c.2392C>T,p.(Arg798Ter). The submitter classified this as a variant of uncertain significance, providing very strong variant effect evidence with the intention of adding supporting pedigree information, according to the guidelines used for classification. However, the relatively high population frequency in the UKB cohort of 367/439 920 (0.083%) was a concern as it is higher than expected for the disease frequency, which would reduce the predicted pathogenicity score. This situation highlights the increasing concerns over the use of population data in pathogenicity classification of truncating/loss-of-function (LoF) variants in known cancer predisposition genes, particularly since the addition of UKB control data. Here, we have conducted a series of case-control comparisons for common truncating variants in known breast/ovarian cancer-associated genes, as well as LZTR1-related schwannomatosis, to address this issue using our Manchester cancer screening population compared with controls in UKB data.Our data show strong ORs for these common truncating variants. We propose that for truncating variants in cancer susceptibility genes with a significant case-control OR, apparently conflicting population frequency evidence criteria should be avoided.

Background: The LSM1 gene encodes a subunit of the conserved LSM1-7 protein complex involved in messenger RNA (mRNA) metabolism. Variants in the LSM1 gene have been described in two separate case reports. The first published report identified the homozygous splice-site variant c.231+4A>C, while the second reported a homozygous missense variant. Nevertheless, variation in LSM1 has yet to be established as disease-causing in humans.

Methods: Through exome sequencing and detailed phenotyping, we report six syndromic paediatric patients with the homozygous c.231+4A>C variant in the LSM1 gene, collected via GeneMatcher. GestaltMatcher was used to analyse facial feature similarity, and real-time quantitative PCR (RT-qPCR) confirmed the splice defect caused by the variant. Haplotype analysis assessed whether this variant resulted from independent occurrences or a common ancestral haplotype.

Results: Patients presented with dysmorphic facial features, developmental delay and multisystemic involvement, including urological, cardiac and skeletal manifestations, showcasing the phenotypic spectrum of this syndrome. RT-qPCR confirmed that the c.231+4A>C variant causes exon 3 skipping, producing negligible wild-type LSM1 mRNA expression. Elevated mutant isoform expression confirmed pathogenicity according to the American College of Medical Genetics and Genomics (ACMG) guidelines. We identified this variant in the Muslim Arab and Ashkenazi Jewish populations and determined that it represents a hotspot variant through haplotype analysis.

Conclusion: Our findings establish LSM1, and specifically the c.231+4A>C homozygous variant, as causative for a novel autosomal recessive syndromic neurodevelopmental disorder. These results expand the understanding of LSM1-related diseases and provide a foundation for further investigation of its molecular mechanisms.